The present invention relates to a novel use of N-acylamino acid derivatives. These compounds, for example those described in the international patent applications published under the numbers WO 92/20647, WO 92/21318, WO 94/26694, WO 94/27561 and WO 98/09611, are, in particular on account of their antimicrobial and antielastic activity, used as active agents in formulations for topical use. Such cosmetic, dermopharmaceutical or pharmaceutical formulations intended to care for the skin or mucous membranes must be easy to take up with the fingers before they are applied; when they are applied on the skin or on mucous membranes, they must spread easily, penetrate quickly and melt in well while at the same time affording sensations of freshness and softness, without being perceived as greasy or oily, and, after they have been applied to the skin or mucous membranes, they must not give rise to any sheen on the skin, or any unpleasant odour, or appear sticky; however, the sensations of softness and freshness resulting from their application must remain.
Now, in order to obtain a sensory profile which satisfies a formulation, it is often necessary to include texturing agents therein, which are compounds or mixtures of compounds capable of improving the rheological and sensory properties of the formulation. The applicant has found, unexpectedly, that N-acylamino acid derivatives can be used effectively as texturing agents for cosmetic, dermopharmaceutical or pharmaceutical formulations.
Accordingly, a subject of the invention is the use of at least one compound of formula (I): 
in which R represents the characterizing chain of a saturated or unsaturated, linear or branched fatty acid, the fragment Rxe2x80x94CO comprises from 12 to 22 carbon atoms and more particularly from 16 to 22 carbon atoms, 
represents the characterizing chain or cyclic radical of an amino acid, R2 represents a hydrogen atom or an alkyl radical comprising from 1 to 3 carbon atoms, or the topically acceptable salts thereof, as texturing agents, it being understood that the amino acid characterized by R1 is not lysine, hydroxylysine or
The expression xe2x80x9ctopically acceptable saltxe2x80x9d means any salt of the acid of formula (I) which is biologically acceptable for the skin and/or mucous membranes, i.e., any salt which can in particular adjust the pH of the composition to a value of between 3 and 8 and preferably approximately equal to 5, which is a pH in the region of the skin""s pH. Examples of such salts are, in particular, alkali metal salts, such as sodium, potassium or lithium salts, alkaline-earth metal salts, such as calcium, magnesium or strontium salts; they can also be metal salts such as divalent zinc, copper or manganese salts or alternatively trivalent iron, lanthanum, cerium or aluminium salts. The compound of formula (I) present in the composition which is the subject of the present invention can be in free acid form or in partially or totally salified form. The expression xe2x80x9ccharacterizing chainxe2x80x9d used in the context of the present patent application denotes the main chain of the fatty acid or of the amino acid under consideration. Thus, for a fatty acid corresponding to the general formula Rxe2x80x94COOH, the characterizing chain will be the chain represented by R. The linear or branched, saturated or unsaturated radical R represents a radical comprising from 11 to 21 carbon atoms, chosen, for example, from undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, uneicosyl, docosyl, heptadecenyl, eicosenyl, uneicosenyl and heptadecadienyl radicals.
A subject of the invention is, more particularly, the use as defined above, for which, in formula (I), the fragment Rxe2x80x94CO represents in particular one of the following radicals: dodecanoyl (lauroyl), tetradecanoyl (myristyl), hexadecanoyl (palmitoyl), octadecanoyl (stearyl), eicosanoyl (arachidoyl), docosanoyl (behenoyl), octadecenoyl (oleyl), eicosenoyl (gadoloyl), docosenoyl (erucyl) or octadecadienoyl (linolenoyl). For an amino acid represented by the general formula;
HN(R2)xe2x80x94CHR1xe2x80x94COOH,
it will be characterized by the definition of R1; for an amino acid represented by the general formula: 
it will be characterized by the definition of the cyclic radical: 
In the context of the present invention, the chain or the cyclic radical characterizing the amino acid are chosen from those of glycine, alanine, serine, aspartic acid, glutamic acid, valine, threonine, proline, leucine, phenylalanine, isoleucine, histidine, tyrosine, tryptophan, asparagine, cysteine, cystine, methionine, hydroxyproline, ornithine and sarcosine. A subject of the invention is, more particularly, the use as described above for which, in formula (I), the chain or the cyclic radical characterizing the amino acid are chosen from those of glycine, proline, glutamic acid and sarcosine.
The expression xe2x80x9cat least one compound of formula (I)xe2x80x9d means that the invention can be carried out with one or more of these compounds. The expression xe2x80x9cor more of these compoundsxe2x80x9d means:
either a mixture of compounds of formula (I), resulting from the condensation of a single amino acid with a mixture of fatty acids, and more particularly a mixture of fatty acids of natural origin, or a mixture of compounds of formula (I) resulting from the condensation of a mixture of amino acids with a single fatty acid, or a mixture of compounds of formula (I) resulting from the condensation of a mixture of amino *acids with a mixture of fatty acids, and more particularly with a mixture of fatty acids of natural origin. The mixtures of fatty acids of natural origin which can be used advantageously for the preparation of the compounds of formula (I) are, in particular, those derived from coconut oil, palm kernel oil, palm oil, soybean oil, rapeseed oil, bovine tallow, spermaceti oil, herring oil or castor oil.
According to a very specific aspect of the present invention, its subject is the use, as described above, of a mixture comprising at least one compound of formula (Ia) corresponding to formula (I), in which the cyclic radical characterizing the amino acid is that of praline, and at least one compound of formula (Ib) corresponding to formula (I) in which the characterizing chain of the amino acid is that of glutamic acid, and optionally at least one compound of formula (Ic) corresponding to formula (I) in which R2 represents a methyl radical and R1 represents the characterizing chain of sarcosine; as an example of such a use, mention may be made of the use of the mixture comprising N-palmitoylproline and N-palmitoylglutamic acid or the sodium or magnesium salts thereof or the use of the mixture comprising N-palmitoylproline, N-palmitoylglutamic acid and N-palmitoylsarcosine or the sodium or magnesium salts thereof.
According to another very specific aspect of the present invention, its subject is the use, as described above, of a composition comprising N-cocoylglycine or one of the topically acceptable salts thereof.
The compounds of formula (I) are obtained by the methods known to those skilled in the art and described in particular in the international patent applications published under the numbers WO 92/20647, WO 92/21318, WO 94/26694, WO 94/27561 and WO 98109611.
A subject of the invention is also a composition (A) comprising;
a) from 10% to 95% by weight, and more particularly from 60% to 80% by weight, of at least one compound of formula (I): 
xe2x80x83in which R represents the characterizing chain of a saturated or unsaturated, linear or branched fatty acid comprising from 12 to 22 carbon atoms, 
xe2x80x83represents the chain or the cyclic radical characterizing the amino acid, chosen from those of glycine, alanine, serine, aspartic acid, glutamic acid, valine, threonine, proline, leucine, phenylalanine, isoleucine, histidine, tyrosine, tryptophan, asparagine, cysteine, cystine, methionine, hydroxyproline, ornithine and sarcosine, R, represents a hydrogen atom or an alkyl radical comprising from 1 to 3 carbon atoms, or one of the topically acceptable salts thereof, and R2 represents a hydrogen atom or an alkyl radical comprising from 1 to 3 carbon atoms, or one of the topically acceptable salts thereof, and
b) from 90% to 5% by weight of at least one compound of formula (II)
Rxe2x80x94COxe2x80x94OH,
or one of the topically acceptable salts thereof.
A subject of the invention is, more particularly, a composition (A) as defined above, for which the radical R comprises from 16 to 22 carbon atoms, and more particularly from 16 to 18 carbon atoms. According to one very specific aspect of the present invention, its subject is the composition (A) as defined above, comprising:
from 30% to 50% by weight of palmitoylproline,
from 5% to 25% by weight of N-palmitoylglutamic acid,
from 0% to 25% by weight of N-palmitoylsarcosine and
from about 5% to about 40% by weight of palmitic acid.
According to another very specific aspect of the present invention, its subject is the composition (A) as defined above, comprising:
from 30% to 70% by weight of cocoylglycine,
from 0% to 25% by weight of N-cocoylsarcosine and
from about 5% to about 45% by weight, and more particularly from 5% to about 20% by weight, of the mixture of fatty acids derived from coconut oil.
A subject of the present invention is also a cosmetic, dermopharmaceutical or pharmaceutical formulation comprising, as texturing agent, an effective amount of at least one compound of formula I as defined above. In the context of the present invention, the expression xe2x80x9ceffective amountxe2x80x9d means an amount representing from about 0.1% to about 5% by weight of the formulation.
The cosmetic formulation is usually in the form of an aqueous solution, a dilute alcoholic solution or a simple or multiple emulsion, such as a water-in-oil (W/O), oil-in-water (O/W) or water-in-oil-in-water (W/O/W) emulsion, or a dispersion of liposomes or of aminosomes. The term xe2x80x9caminosomexe2x80x9d denotes a type of liposome formed by amphiphilic amino acid derivatives. Examples which may be mentioned are creams, milks, lotions, antisun emulsions, cosmetic wipes, gels such as shower gels or cream-gels, oils, soaps, liquid soaps, syndets, intimate-hygiene products, shampoos, make-up powders and mascaras.
A subject of the invention is also the use of a composition (A) as defined above, to prepare a cosmetic, dermopharmaceutical or pharmaceutical formulation. This formulation is prepared according to the methods known to those skilled in the art which are suitable for the desired type of formulation, by combining composition (A) with the usual cosmetic active agents and excipients.
The compounds of formula (I) are compatible with most known excipients, whether this is, for example, with reverse latices such as the compounds sold under the names Sepigel(trademark) 305, sepigel(trademark) 501, Sepigel(trademark) 502, Simulgel(trademark) 600, SiMulgel(trademark) A or Simulgel(trademark) EG, or with the compositions sold under the names Montanov(trademark) 68, Montanov(trademark) 14, Montanov(trademark) 82, Montanov(trademark) 202 or Sepigel(trademark) N and described, for example, in the patent applications published under the numbers WO 92/02778, WO 95/13863, WO 96/37285, WO 98/22207 or WO 98/47610.
The examples which follow illustrate the invention without, however, limiting it.